The objective of this proposal is to examine the mechanism by which the transforming gene, src, encoded by Rous sarcoma virus alters the expression of normal cellular genes. The model system utilizes chicken embryo chondrogenic cells infected with ts-src mutants of Rous sarcoma virus. We have demonstrated that transformation induces changes in the synthesis of proteoglycans, collagens, fibrorectin, and hyaluronic acid. Here we will focus on the synthesis of the chondroblast specific type II collagen propeptide Alpha I(II) which is switched off by transformation and fibrorectin and the type I collagen propeptides Alpha 1(I) and Alpha 2(I) which are switched on. The levels of analysis include analysis of synthesis of the gene products, synthesis and processing of the specific m-RNA's, and analysis of DNase I sensitivity and methylation of the specific DNA coding regions. The mechanism by which the altered expression is achieved by RSV-induced cell transformation will be compared to (a) changes in gene expression during normal chondrogenic differentiation, (b) other physical and chemical treatments which induce analogous alterations in chondroblasts, and (c) changes induced by src variants, other sarcoma virus strains, and leukemogenic viruses. This comparative approach combined with drug inhibition studies and kinetics of the various transitions will be used to refine and examine the hypotheses on the mechanism of src action.